Growth hormone (GH), also known as somatotropin (or as human growth hormone [hGH or HGH] in its human form), is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in human development, it is a type of mitogen which is specific only to certain kinds of cells. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland.

GH is a stress hormone that raises the concentration of glucose and free fatty acids,[1][2] it also stimulates production of IGF-1.

A recombinant form of hGH called somatropin (INN) is used as a prescription drug to treat children's growth disorders and adult growth hormone deficiency. In the United States, it is only available legally from pharmacies, by prescription from a doctor; in recent years in the United States, some doctors have started to prescribe growth hormone in GH-deficient older patients (but not on healthy people) to increase vitality. While legal, the efficacy and safety of this use for HGH has not been tested in a clinical trial, at this time, HGH is still considered a very complex hormone, and many of its functions are still unknown.[3]

In its role as an anabolic agent, HGH has been used by competitors in sports since at least 1982, and has been banned by the IOC and NCAA. Traditional urine analysis does not detect doping with HGH, so the ban was unenforceable until the early 2000s, when blood tests that could distinguish between natural and artificial HGH were starting to be developed. Blood tests conducted by WADA at the 2004 Olympic Games in Athens, Greece targeted primarily HGH.[3] Use of the drug for performance enhancement is not currently approved by the FDA.

GH has been studied for use in raising livestock more efficiently in industrial agriculture and several efforts have been made to obtain governmental approval to use GH in livestock production, these uses have been controversial. In the United States, the only FDA-approved use of GH for livestock is the use of a cow-specific form of GH called bovine somatotropin for increasing milk production in dairy cows. Retailers are permitted to label containers of milk as produced with or without bovine somatotropin.

The names somatotropin (STH) or somatotropic hormone refer to the growth hormone produced naturally in animals and extracted from carcasses. Hormone extracted from human cadavers is abbreviated hGH, the main growth hormone produced by recombinant DNA technology has the approved generic name somatropin (INN) and the brand name Humatrope,[4] and is properly abbreviated rhGH in the scientific literature. Since its introduction in 1992 Humatrope has been a banned sports doping agent,[5] and in this context is referred to as HGH.

The major isoform of the human growth hormone is a protein of 191 amino acids and a molecular weight of 22,124 daltons, the structure includes four helices necessary for functional interaction with the GH receptor. It appears that, in structure, GH is evolutionarily homologous to prolactin and chorionic somatomammotropin, despite marked structural similarities between growth hormone from different species, only human and Old World monkey growth hormones have significant effects on the human growth hormone receptor.[8]

Several molecular isoforms of GH exist in the pituitary gland and are released to blood; in particular, a variant of approximately 20 kDa originated by an alternative splicing is present in a rather constant 1:9 ratio,[9] while recently an additional variant of ~ 23-24 kDa has also been reported in post-exercise states at higher proportions.[10] This variant has not been identified, but it has been suggested to coincide with a 22 kDa glycosylated variant of 23 kDa identified in the pituitary gland.[11] Furthermore, these variants circulate partially bound to a protein (growth hormone-binding protein, GHBP), which is the truncated part of the growth hormone receptor, and an acid-labile subunit (ALS).

Secretion of growth hormone (GH) in the pituitary is regulated by the neurosecretory nuclei of the hypothalamus, these cells release the peptides Growth hormone-releasing hormone (GHRH or somatocrinin) and Growth hormone-inhibiting hormone (GHIH or somatostatin) into the hypophyseal portal venous blood surrounding the pituitary. GH release in the pituitary is primarily determined by the balance of these two peptides, which in turn is affected by many physiological stimulators (e.g., exercise, nutrition, sleep) and inhibitors (e.g., free fatty acids) of GH secretion.[12]

Somatotropic cells in the anterior pituitary gland then synthesize and secrete GH in a pulsatile manner, in response to these stimuli by the hypothalamus. The largest and most predictable of these GH peaks occurs about an hour after onset of sleep with plasma levels of 13 to 72 ng/mL.[13] Otherwise there is wide variation between days and individuals. Nearly fifty percent of GH secretion occurs during the third and fourth NREM sleep stages.[14] Surges of secretion during the day occur at 3- to 5-hour intervals,[3] the plasma concentration of GH during these peaks may range from 5 to even 45 ng/mL.[15] Between the peaks, basal GH levels are low, usually less than 5 ng/mL for most of the day and night.[13] Additional analysis of the pulsatile profile of GH described in all cases less than 1 ng/ml for basal levels while maximum peaks were situated around 10-20 ng/mL.[16][17]

A number of factors are known to affect GH secretion, such as age, sex, diet, exercise, stress, and other hormones.[3] Young adolescents secrete GH at the rate of about 700 μg/day, while healthy adults secrete GH at the rate of about 400 μg/day.[18] Sleep deprivation generally suppresses GH release, particularly after early adulthood.[19]

Effects of growth hormone on the tissues of the body can generally be described as anabolic (building up). Like most other protein hormones, GH acts by interacting with a specific receptor on the surface of cells.

Increased height during childhood is the most widely known effect of GH. Height appears to be stimulated by at least two mechanisms:

The most common disease of GH excess is a pituitary tumor composed of somatotroph cells of the anterior pituitary, these somatotroph adenomas are benign and grow slowly, gradually producing more and more GH. For years, the principal clinical problems are those of GH excess. Eventually, the adenoma may become large enough to cause headaches, impair vision by pressure on the optic nerves, or cause deficiency of other pituitary hormones by displacement.

Prolonged GH excess thickens the bones of the jaw, fingers and toes. Resulting heaviness of the jaw and increased size of digits is referred to as acromegaly. Accompanying problems can include sweating, pressure on nerves (e.g., carpal tunnel syndrome), muscle weakness, excess sex hormone-binding globulin (SHBG), insulin resistance or even a rare form of type 2 diabetes, and reduced sexual function.

GH-secreting tumors are typically recognized in the fifth decade of life, it is extremely rare for such a tumor to occur in childhood, but, when it does, the excessive GH can cause excessive growth, traditionally referred to as pituitary gigantism.

Surgical removal is the usual treatment for GH-producing tumors; in some circumstances, focused radiation or a GH antagonist such as pegvisomant may be employed to shrink the tumor or block function. Other drugs like octreotide (somatostatin agonist) and bromocriptine (dopamine agonist) can be used to block GH secretion because both somatostatin and dopamine negatively inhibit GHRH-mediated GH release from the anterior pituitary.[citation needed]

Adults with GHD "tend to have a relative increase in fat mass and a relative decrease in muscle mass and, in many instances, decreased energy and quality of life".[40]

Diagnosis of GH deficiency involves a multiple-step diagnostic process, usually culminating in GH stimulation tests to see if the patient's pituitary gland will release a pulse of GH when provoked by various stimuli.

Several studies, primarily involving patients with GH deficiency, have suggested a crucial role of GH in both mental and emotional well-being and maintaining a high energy level. Adults with GH deficiency often have higher rates of depression than those without.[41] While GH replacement therapy has been proposed to treat depression as a result of GH deficiency, the long-term effects of such therapy are unknown.[41]

GH has also been studied in the context of cognitive function, including learning and memory.[42] GH in humans appears to improve cognitive function and may be useful in the treatment of patients with cognitive impairment that is a result of GH deficiency.[42]

Treatment with exogenous GH is indicated only in limited circumstances,[40] and needs regular monitoring due to the frequency and severity of side-effects. GH is used as replacement therapy in adults with GH deficiency of either childhood-onset or adult-onset (usually as a result of an acquired pituitary tumor); in these patients, benefits have variably included reduced fat mass, increased lean mass, increased bone density, improved lipid profile, reduced cardiovascular risk factors, and improved psychosocial well-being.

GH can be used to treat conditions that produce short stature but are not related to deficiencies in GH. However, results are not as dramatic when compared to short stature that is solely attributable to deficiency of GH. Examples of other causes of shortness often treated with GH are Turner syndrome, chronic renal failure, Prader–Willi syndrome, intrauterine growth restriction, and severe idiopathic short stature. Higher ("pharmacologic") doses are required to produce significant acceleration of growth in these conditions, producing blood levels well above normal ("physiologic"), despite the higher doses, side-effects during treatment are rare, and vary little according to the condition being treated.

One version of rHGH has also been FDA approved for maintaining muscle mass in wasting due to AIDS.[43]

Off-label prescription of HGH is controversial and may be illegal.[44]

Claims for GH as an anti-aging treatment date back to 1990 when the New England Journal of Medicine published a study wherein GH was used to treat 12 men over 60.[45] At the conclusion of the study, all the men showed statistically significant increases in lean body mass and bone mineral density, while the control group did not, the authors of the study noted that these improvements were the opposite of the changes that would normally occur over a 10- to 20-year aging period. Despite the fact the authors at no time claimed that GH had reversed the aging process itself, their results were misinterpreted as indicating that GH is an effective anti-aging agent.[46][47][48] This has led to organizations such as the controversial American Academy of Anti-Aging Medicine promoting the use of this hormone as an "anti-aging agent".[49]

A Stanford University School of Medicine meta-analysis of clinical studies on the subject published in early 2007 showed that the application of GH on healthy elderly patients increased muscle by about 2 kg and decreased body fat by the same amount.[46] However, these were the only positive effects from taking GH. No other critical factors were affected, such as bone density, cholesterol levels, lipid measurements, maximal oxygen consumption, or any other factor that would indicate increased fitness.[46] Researchers also did not discover any gain in muscle strength, which led them to believe that GH merely let the body store more water in the muscles rather than increase muscle growth, this would explain the increase in lean body mass.

The Drug Enforcement Administration of the US Department of Justice considers off-label prescribing of HGH to be illegal, and to be a key path for illicit distribution of HGH.[44] This section has also been interpreted by some doctors, most notably[52] the authors of a commentary article published in the Journal of the American Medical Association in 2005, as meaning that prescribing HGH off-label may be considered illegal.[53] And some articles in the popular press, such as those criticizing the pharmaceutical industry for marketing drugs for off-label use (which is clearly illegal) have made strong statements about whether doctors can prescribe HGH off-label: "Unlike other prescription drugs, HGH may be prescribed only for specific uses. U.S. sales are limited by law to treat a rare growth defect in children and a handful of uncommon conditions like short bowel syndrome or Prader-Willi syndrome, a congenital disease that causes reduced muscle tone and a lack of hormones in sex glands."[54][55] At the same time, anti-aging clinics where doctors prescribe, administer, and sell HGH to people are big business;[54][56] in a 2012 article in Vanity Fair, when asked how HGH prescriptions far exceed the number of adult patients estimated to have HGH-deficiency, Dragos Roman, who leads a team at the FDA that reviews drugs in endocrinology, said "The F.D.A. doesn't regulate off-label uses of H.G.H. Sometimes it's used appropriately. Sometimes it's not."[56]

Use of GH as a drug has been approved by the FDA for several indications, this means that the drug has acceptable safety in light of its benefits when used in the approved way. Like every drug, there are several side effects caused by GH, some common, some rare. Injection-site reaction is common. More rarely, patients can experience joint swelling, joint pain, carpal tunnel syndrome, and an increased risk of diabetes;[46] in some cases, the patient can produce an immune response against GH. GH may also be a risk factor for Hodgkin's lymphoma.[57]

One survey of adults that had been treated with replacement cadaver GH (which has not been used anywhere in the world since 1985) during childhood showed a mildly increased incidence of colon cancer and prostate cancer, but linkage with the GH treatment was not established.[58]

The first description of the use of GH as a doping agent was Dan Duchaine's "Underground Steroid handbook" which emerged from California in 1982; it is not known where and when GH was first used this way.[59]

Athletes in many sports have used human growth hormone in order to attempt to enhance their athletic performance, some recent studies have not been able to support claims that human growth hormone can improve the athletic performance of professional male athletes.[60][61][62] Many athletic societies ban the use of GH and will issue sanctions against athletes who are caught using it. However, because GH is a potent endogenous protein, it is very difficult to detect GH doping; in the United States, GH is legally available only by prescription from a medical doctor.

To capitalize on the idea that GH might be useful to combat aging, companies selling dietary supplements have websites selling products linked to GH in the advertising text, with medical-sounding names described as "HGH Releasers". Typical ingredients include amino acids, minerals, vitamins, and/or herbal extracts, the combination of which are described as causing the body to make more GH with corresponding beneficial effects; in the United States, because these products are marketed as dietary supplements it is illegal for them to contain GH, which is a drug. Also, under United States law, products sold as dietary supplements cannot have claims that the supplement treats or prevents any disease or condition, and the advertising material must contain a statement that the health claims are not approved by the FDA, the FTC and the FDA do enforce the law when they become aware of violations.[63]

The identification, purification and later synthesis of growth hormone is associated with Choh Hao Li. Genentech pioneered the first use of recombinant human growth hormone for human therapy in 1981.

Prior to its production by recombinant DNA technology, growth hormone used to treat deficiencies was extracted from the pituitary glands of cadavers. Attempts to create a wholly synthetic HGH failed. Limited supplies of HGH resulted in the restriction of HGH therapy to the treatment of idiopathic short stature.[69] Very limited clinical studies of growth hormone derived from an Old World monkey, the rhesus macaque, were conducted by John C. Beck and colleagues in Montreal, in the late 1950s,[70] the study published in 1957, which was conducted on "a 13-year-old male with well-documented hypopituitarism secondary to a crainiophyaryngioma," found that: "Human and monkey growth hormone resulted in a significant enhancement of nitrogen storage ... (and) there was a retention of potassium, phosphorus, calcium, and sodium. ... There was a gain in body weight during both periods. ... There was a significant increase in urinary excretion of aldosterone during both periods of administration of growth hormone, this was most marked with the human growth hormone. ... Impairment of the glucose tolerance curve was evident after 10 days of administration of the human growth hormone. No change in glucose tolerance was demonstrable on the fifth day of administration of monkey growth hormone."[70] The other study, published in 1958, was conducted on six people: the same subject as the Science paper; an 18-year-old male with statural and sexual retardation and a skeletal age of between 13 and 14 years; a 15-year-old female with well-documented hypopituitarism secondary to a craniopharyngioma; a 53-year-old female with carcinoma of the breast and widespread skeletal metastases; a 68-year-old female with advanced postmenopausal osteoporosis; and a healthy 24-year-old medical student without any clinical or laboratory evidence of systemic disease.[71]

In 1985, unusual cases of Creutzfeldt–Jakob disease were found in individuals that had received cadaver-derived HGH ten to fifteen years previously. Based on the assumption that infectious prions causing the disease were transferred along with the cadaver-derived HGH, cadaver-derived HGH was removed from the market.[18]

In 1985, biosynthetic human growth hormone replaced pituitary-derived human growth hormone for therapeutic use in the U.S. and elsewhere.

As of 2005, recombinant growth hormones available in the United States (and their manufacturers) included Nutropin (Genentech), Humatrope (Lilly), Genotropin (Pfizer), Norditropin (Novo), and Saizen (Merck Serono). In 2006, the U.S. Food and Drug Administration (FDA) approved a version of rHGH called Omnitrope (Sandoz).[72] A sustained-release form of growth hormone, Nutropin Depot (Genentech and Alkermes) was approved by the FDA in 1999, allowing for fewer injections (every 2 or 4 weeks instead of daily); however, the product was discontinued by Genentech/Alkermes in 2004 for financial reasons (Nutropin Depot required significantly more resources to produce than the rest of the Nutropin line[73]).

^ abDEA, US Department of Justice. DEA: Genotropin Quote: "The illicit distribution of hGH occurs as the result of physicians illegally prescribing it for off-label uses, and for the treatment of FDA-approved medical conditions without examination and supervision"

1.
Growth hormone 1
–
Somatotropin is a protein that in humans is encoded by the GH1 gene. The protein encoded by this gene is a member of the family of hormones that play an important role in growth control. The five genes share a high degree of sequence identity. Alternative splicing generates additional isoforms of each of the five growth hormones, leading to further diversity and this particular family member is expressed in the pituitary but not in placental tissue as is the case for the other four genes in the growth hormone locus. Mutations in or deletions of the lead to growth hormone deficiency

2.
Entrez
–
The name Entrez was chosen to reflect the spirit of welcoming the public to search the content available from the NLM. Entrez Global Query is a search and retrieval system that provides access to all databases simultaneously with a single query string. Entrez can efficiently retrieve related sequences, structures, and references, the Entrez system can provide views of gene and protein sequences and chromosome maps. Some textbooks are available online through the Entrez system. The Entrez front page provides, by default, access to the global query, all databases indexed by Entrez can be searched via a single query string, supporting boolean operators and search term tags to limit parts of the search statement to particular fields. This returns a unified results page, that shows the number of hits for the search in each of the databases, Entrez also provides a similar interface for searching each particular database and for refining search results. The Limits feature allows the user to narrow a search a web forms interface, the History feature gives a numbered list of recently performed queries. Results of previous queries can be referred to by number and combined via boolean operators, search results can be saved temporarily in a Clipboard. Users with a MyNCBI account can save queries indefinitely and also choose to have updates with new search results e-mailed for saved queries of most databases and it is widely used in the field of biotechnology as a reference tool for students and professionals alike. Entrez searches the following databases, PubMed, biomedical literature citations and abstracts, including Medline - articles from journals, in addition to using the search engine forms to query the data in Entrez, NCBI provides the Entrez Programming Utilities for more direct access to query results. The eUtils are accessed by posting specially formed URLs to the NCBI server, there was also an eUtils SOAP interface which was terminated on July 2015. In 1991, entrez was introduced in CD form, in 1993, a client-server version of the software provided connectivity with the internet. In 1994, NCBI established a website, and Entrez was a part of initial release. In 2001, Entrez bookshelf was released and in 2003, the Entrez Gene database was developed, Entrez search engine form Entrez Help

3.
National Center for Biotechnology Information
–
The National Center for Biotechnology Information is part of the United States National Library of Medicine, a branch of the National Institutes of Health. The NCBI is located in Bethesda, Maryland and was founded in 1988 through legislation sponsored by Senator Claude Pepper, the NCBI houses a series of databases relevant to biotechnology and biomedicine and is an important resource for bioinformatics tools and services. Major databases include GenBank for DNA sequences and PubMed, a database for the biomedical literature. Other databases include the NCBI Epigenomics database, all these databases are available online through the Entrez search engine. NCBI is directed by David Lipman, one of the authors of the BLAST sequence alignment program. He also leads a research program, including groups led by Stephen Altschul, David Landsman, Eugene Koonin, John Wilbur, Teresa Przytycka. NCBI is listed in the Registry of Research Data Repositories re3data. org, NCBI has had responsibility for making available the GenBank DNA sequence database since 1992. GenBank coordinates with individual laboratories and other databases such as those of the European Molecular Biology Laboratory. Since 1992, NCBI has grown to other databases in addition to GenBank. The NCBI assigns a unique identifier to each species of organism, the NCBI has software tools that are available by WWW browsing or by FTP. For example, BLAST is a sequence similarity searching program, BLAST can do sequence comparisons against the GenBank DNA database in less than 15 seconds. RAG2/IL2RG The NCBI Bookshelf is a collection of freely accessible, downloadable, some of the books are online versions of previously published books, while others, such as Coffee Break, are written and edited by NCBI staff. BLAST is a used for calculating sequence similarity between biological sequences such as nucleotide sequences of DNA and amino acid sequences of proteins. BLAST is a tool for finding sequences similar to the query sequence within the same organism or in different organisms. It searches the query sequence on NCBI databases and servers and post the results back to the browser in chosen format. Input sequences to the BLAST are mostly in FASTA or Genbank format while output could be delivered in variety of such as HTML, XML formatting. HTML is the output format for NCBIs web-page. Entrez is both indexing and retrieval system having data from sources for biomedical research

4.
UniProt
–
UniProt is a freely accessible database of protein sequence and functional information, many entries being derived from genome sequencing projects. It contains an amount of information about the biological function of proteins derived from the research literature. The UniProt consortium comprises the European Bioinformatics Institute, the Swiss Institute of Bioinformatics, EBI, located at the Wellcome Trust Genome Campus in Hinxton, UK, hosts a large resource of bioinformatics databases and services. SIB, located in Geneva, Switzerland, maintains the ExPASy servers that are a resource for proteomics tools. In 2002, EBI, SIB, and PIR joined forces as the UniProt consortium, each consortium member is heavily involved in protein database maintenance and annotation. Until recently, EBI and SIB together produced the Swiss-Prot and TrEMBL databases and these databases coexisted with differing protein sequence coverage and annotation priorities. Swiss-Prot aimed to provide reliable protein sequences associated with a level of annotation. Recognizing that sequence data were being generated at a pace exceeding Swiss-Prots ability to keep up, meanwhile, PIR maintained the PIR-PSD and related databases, including iProClass, a database of protein sequences and curated families. The consortium members pooled their resources and expertise, and launched UniProt in December 2003. UniProt provides four core databases, UniProtKB, UniParc, UniRef, UniProt Knowledgebase is a protein database partially curated by experts, consisting of two sections, UniProtKB/Swiss-Prot and UniProtKB/TrEMBL. As of 19 March 2014, release 2014_03 of UniProtKB/Swiss-Prot contains 542,782 sequence entries, UniProtKB/Swiss-Prot is a manually annotated, non-redundant protein sequence database. It combines information extracted from literature and biocurator-evaluated computational analysis. The aim of UniProtKB/Swiss-Prot is to all known relevant information about a particular protein. Annotation is regularly reviewed to keep up with current scientific findings, the manual annotation of an entry involves detailed analysis of the protein sequence and of the scientific literature. Sequences from the gene and the same species are merged into the same database entry. Differences between sequences are identified, and their cause documented, a range of sequence analysis tools is used in the annotation of UniProtKB/Swiss-Prot entries. Computer-predictions are manually evaluated, and relevant results selected for inclusion in the entry and these predictions include post-translational modifications, transmembrane domains and topology, signal peptides, domain identification, and protein family classification. Relevant publications are identified by searching databases such as PubMed, the full text of each paper is read, and information is extracted and added to the entry

5.
Locus (genetics)
–
A locus in genetics is the position on a chromosome. Each chromosome carries many genes, humans estimated haploid protein coding genes are 19, 000-20,000, a variant of the similar DNA sequence located at a given locus is called an allele. The ordered list of known for a particular genome is called a gene map. Gene mapping is the process of determining the locus for a biological trait. The chromosomal locus of a gene might be written 3p22.1, here 3 means chromosome 3, p means p-arm. And 22 refers to region 2, band 2 and this is read as two two, not as twenty-two. So the entire locus is read as three P two two point one, the cytogenetic bands are counting from the centromere out toward the telomeres. A range of loci is specified in a similar way. For example, the locus of gene OCA1 may be written 11q1. 4-q2.1, meaning it is on the arm of chromosome 11. The ends of a chromosome are labeled pter and qter, a centisome is defined as 1% of a chromosome length. Chromosomal translocation Cytogenetic notation Karyotype Null allele Michael, R. Cummings, belmont, California, Brooks/Cole Overview at ornl. gov Chromosome Banding and Nomenclature from NCBI

6.
Chromosome 17 (human)
–
Chromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome, chromosome 17 spans more than 83 million base pairs and represents between 2.5 and 3% of the total DNA in cells. Identifying genes on each chromosome is an area of genetic research. Because researchers use different approaches to genome annotation their predictions of the number of genes on each chromosome varies, in January 2017, two estimates differed by 9%, with one estimate giving 2,432 genes, and the other estimate giving 2,653 genes. Chromosome 17 contains the Homeobox B gene cluster, disease genes and chromosomes, disease maps of the human genome

7.
Growth hormone 2
–
Growth hormone variant is a protein that in humans is encoded by the GH2 gene. The protein encoded by this gene is a member of the family of hormones. The five genes share a high degree of sequence identity. Alternative splicing generates additional isoforms of each of the five growth hormones, leading to further diversity, as in the case of its pituitary counterpart, growth hormone 1, the predominant isoform of this particular family member shows similar somatogenic activity, with reduced lactogenic activity. Mutations in this lead to placental growth hormone/lactogen deficiency

8.
Cell (biology)
–
The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life that can replicate independently, the study of cells is called cell biology. Cells consist of cytoplasm enclosed within a membrane, which contains many such as proteins. Organisms can be classified as unicellular or multicellular, while the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion cells. Most plant and animal cells are only under a microscope. The cell was discovered by Robert Hooke in 1665, who named the unit for its resemblance to cells inhabited by Christian monks in a monastery. Cells emerged on Earth at least 3.5 billion years ago, Cells are of two types, eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular, prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling and being self-sustaining. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus, prokaryotes include two of the domains of life, bacteria and archaea. The DNA of a prokaryotic cell consists of a chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid, most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. Though most prokaryotes have both a cell membrane and a wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, the cell wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment, some eukaryotic cells also have a cell wall. Inside the cell is the region that contains the genome, ribosomes. The genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular, linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid, plasmids encode additional genes, such as antibiotic resistance genes

9.
Human development (biology)
–
Human development is the process of growing to maturity. In biological terms, this entails growth from a zygote to an adult human being. Fertilization occurs when the sperm enters the ovums membrane. The genetical material of the sperm and egg that combine to form a cell, called a zygote. The germinal stage refers to the time from fertilization, through the development of the early embryo, the germinal stage is over at about 10 days of gestation. The zygote contains a full complement of genetic material and develops into the embryo, briefly, embryonic developments have four stages, the morula stage, the bastula stage, the gastrula stage, and the neurula stage. Prior to implantation, the remains in a protein shell, the zona pellucida. A week after fertilization the embryo still has not grown in size and this induces a decidual reaction, wherein the uterine cells proliferate and surround the embryo thus causing it to become embedded within the uterine tissue. The embryo, meanwhile, proliferates and develops both into embryonic and extra-embryonic tissue, the forming the fetal membranes and the placenta. In humans, the embryo is referred to as a fetus in the stages of prenatal development. The transition from embryo to fetus is arbitrarily defined as occurring 8 weeks after fertilization, in comparison to the embryo, the fetus has more recognizable external features and a set of progressively developing internal organs. A nearly identical process occurs in other species, auxology Child development Developmental biology Embryogenesis Life-history theory

10.
Amino acid
–
Amino acids are organic compounds containing amine and carboxyl functional groups, along with a side chain specific to each amino acid. The key elements of an acid are carbon, hydrogen, oxygen. About 500 amino acids are known and can be classified in many ways, in the form of proteins, amino acids comprise the second-largest component of human muscles, cells and other tissues. Outside proteins, amino acids perform critical roles in such as neurotransmitter transport. In biochemistry, amino acids having both the amine and the acid groups attached to the first carbon atom have particular importance. They are known as 2-, alpha-, or α-amino acids and they include the 22 proteinogenic amino acids, which combine into peptide chains to form the building-blocks of a vast array of proteins. These are all L-stereoisomers, although a few D-amino acids occur in bacterial envelopes, as a neuromodulator, twenty of the proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as standard amino acids. The other two are selenocysteine, and pyrrolysine, pyrrolysine and selenocysteine are encoded via variant codons, for example, selenocysteine is encoded by stop codon and SECIS element. N-formylmethionine is generally considered as a form of methionine rather than as a separate proteinogenic amino acid, codon–tRNA combinations not found in nature can also be used to expand the genetic code and create novel proteins known as alloproteins incorporating non-proteinogenic amino acids. Many important proteinogenic and non-proteinogenic amino acids also play critical roles within the body. Nine proteinogenic amino acids are called essential for humans because they cannot be created from other compounds by the human body, others may be conditionally essential for certain ages or medical conditions. Essential amino acids may also differ between species, because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers, and food technology. Industrial uses include the production of drugs, biodegradable plastics, the first few amino acids were discovered in the early 19th century. In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, cystine was discovered in 1810, although its monomer, cysteine, remained undiscovered until 1884. Glycine and leucine were discovered in 1820, usage of the term amino acid in the English language is from 1898. Proteins were found to yield amino acids after enzymatic digestion or acid hydrolysis, in the structure shown at the top of the page, R represents a side chain specific to each amino acid. The carbon atom next to the group is called the α–carbon. Amino acids containing an amino group bonded directly to the alpha carbon are referred to as amino acids

11.
Peptide
–
Peptides are biologically occurring short chains of amino acid monomers linked by peptide bonds. The covalent chemical bonds are formed when the group of one amino acid reacts with the amine group of another. The shortest peptides are dipeptides, consisting of 2 amino acids joined by a peptide bond, followed by tripeptides, tetrapeptides. A polypeptide is a long, continuous, and unbranched peptide chain, hence, peptides fall under the broad chemical classes of biological oligomers and polymers, alongside nucleic acids, oligosaccharides and polysaccharides, etc. Peptides are distinguished from proteins on the basis of size, all peptides except cyclic peptides have an N-terminal and C-terminal residue at the end of the peptide. Ribosomal peptides Ribosomal peptides are synthesized by translation of mRNA and they are often subjected to proteolysis to generate the mature form. These function, typically in higher organisms, as hormones and signaling molecules, some organisms produce peptides as antibiotics, such as microcins. Since they are translated, the amino acid residues involved are restricted to those utilized by the ribosome, however, these peptides frequently have posttranslational modifications such as phosphorylation, hydroxylation, sulfonation, palmitoylation, glycosylation and disulfide formation. In general, they are linear, although lariat structures have been observed, more exotic manipulations do occur, such as racemization of L-amino acids to D-amino acids in platypus venom. Nonribosomal peptides Nonribosomal peptides are assembled by enzymes that are specific to each peptide, the most common non-ribosomal peptide is glutathione, which is a component of the antioxidant defenses of most aerobic organisms. Other nonribosomal peptides are most common in organisms, plants. These complexes are often out in a similar fashion. These peptides are often cyclic and can have highly complex cyclic structures, since the system is closely related to the machinery for building fatty acids and polyketides, hybrid compounds are often found. The presence of oxazoles or thiazoles often indicates that the compound was synthesized in this fashion, Peptones See also Tryptone Peptones are derived from animal milk or meat digested by proteolysis. In addition to containing small peptides, the material includes fats, metals, salts, vitamins. Peptones are used in nutrient media for growing bacteria and fungi, Peptide fragments Peptide fragments refer to fragments of proteins that are used to identify or quantify the source protein. Peptides received prominence in molecular biology for several reasons, the first is that peptides allow the creation of peptide antibodies in animals without the need of purifying the protein of interest. This involves synthesizing antigenic peptides of sections of the protein of interest and these will then be used to make antibodies in a rabbit or mouse against the protein

12.
IGF-1
–
Insulin-like growth factor 1, also called somatomedin C, is a protein that in humans is encoded by the IGF1 gene. IGF-1 has also referred to as a sulfation factor and its effects were termed nonsuppressible insulin-like activity in the 1970s. IGF-1 is a similar in molecular structure to insulin. It plays an important role in growth and continues to have anabolic effects in adults. A synthetic analog of IGF-1, mecasermin, is used for the treatment of growth failure, IGF-1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges. IGF-1 has a weight of 7,649 Dalton. IGF-1 is produced primarily by the liver as an endocrine hormone as well as in tissues in a paracrine/autocrine fashion. Approximately 98% of IGF-1 is always bound to one of 6 binding proteins, IGFBP-3, the most abundant protein, accounts for 80% of all IGF binding. IGF-1 binds to IGFBP-3 in a 1,1 molar ratio, the highest rates of IGF-1 production occur during the pubertal growth spurt. The lowest levels occur in infancy and old age, protein intake increases IGF-1 levels in humans, independent of total calorie consumption. IGF-1 is a mediator of the effects of growth hormone. Growth hormone is made in the pituitary gland, is released into the blood stream. In addition to the effects, IGF-1 can also regulate cell growth and development, especially in nerve cells. Its primary action is mediated by binding to its receptor, the insulin-like growth factor 1 receptor. IGF-1 binds to at least two cell surface receptors, the IGF-1 receptor, and the insulin receptor, the IGF-1 receptor seems to be the physiologic receptor – it binds IGF-1 at significantly higher affinity than the IGF-1 that is bound to the insulin receptor. Like the insulin receptor, the IGF-1 receptor is a tyrosine kinase – meaning it signals by causing the addition of a phosphate molecule on particular tyrosines. IGF-1 activates the receptor at approximately 0.1 times the potency of insulin. Part of this signaling may be via IGF1R/Insulin Receptor heterodimers, insulin-like growth factor 1 has been shown to bind and interact with all the IGF-1 binding proteins, of which there are seven, IGFBP1, IGFBP2, IGFBP3, IGFBP4, IGFBP5, IGFBP6, and IGFBP7

13.
Recombinant DNA
–
Recombinant DNA is possible because DNA molecules from all organisms share the same chemical structure. They differ only in the sequence within that identical overall structure. Recombinant DNA is the name for a piece of DNA that has been created by the combination of at least two strands. Recombinant DNA molecules are called chimeric DNA, because they can be made of material from two different species, like the mythical chimera. R-DNA technology uses palindromic sequences and leads to the production of sticky, the DNA sequences used in the construction of recombinant DNA molecules can originate from any species. For example, plant DNA may be joined to bacterial DNA, in addition, DNA sequences that do not occur anywhere in nature may be created by the chemical synthesis of DNA, and incorporated into recombinant molecules. Using recombinant DNA technology and synthetic DNA, literally any DNA sequence may be created and introduced into any of a wide range of living organisms. Proteins that can result from the expression of recombinant DNA within living cells are termed recombinant proteins, when recombinant DNA encoding a protein is introduced into a host organism, the recombinant protein is not necessarily produced. Expression of foreign proteins requires the use of specialized expression vectors, molecular cloning is the laboratory process used to create recombinant DNA. It is one of two widely used methods, along with polymerase chain reaction, used to direct the replication of any specific DNA sequence chosen by the experimentalist, there are two fundamental differences between the methods. One is that cloning involves replication of the DNA within a living cell, while PCR replicates DNA in the test tube. The other difference is that cloning involves cutting and pasting DNA sequences, formation of recombinant DNA requires a cloning vector, a DNA molecule that replicates within a living cell. The choice of vector for molecular cloning depends on the choice of host organism, the size of the DNA to be cloned, the DNA segments can be combined by using a variety of methods, such as restriction enzyme/ligase cloning or Gibson assembly. These steps are described in detail in a related article. Following transplantation into the host organism, the foreign DNA contained within the recombinant DNA construct may or may not be expressed and that is, the DNA may simply be replicated without expression, or it may be transcribed and translated and a recombinant protein is produced. Specific changes to the host organism may be made to improve expression of the ectopic gene, in most cases, organisms containing recombinant DNA have apparently normal phenotypes. Significant exceptions exist, and are discussed below, gross phenotypic changes are not the norm, unless the recombinant gene has been chosen and modified so as to generate biological activity in the host organism. In some cases, recombinant DNA can have deleterious effects even if it is not expressed, one mechanism by which this happens is insertional inactivation, in which the rDNA becomes inserted into a host cells gene

14.
Prescription drug
–
A prescription drug is a pharmaceutical drug that legally requires a medical prescription to be dispensed. In contrast, over-the-counter drugs can be obtained without a prescription, the reason for this difference in substance control is the potential scope of misuse, from drug abuse to practicing medicine without a license and without sufficient education. Different jurisdictions have different definitions of what constitutes a prescription drug, rx is often used as a short form for prescription drug in North America- a contraction of the Latin word recipe meaning take. Prescription drugs are often dispensed together with a monograph that gives detailed information about the drug, the use of prescription drugs has been increasing since the 1960s. In the U. S. 88% of older adults use at least 1 prescription drug, who is able to prescribe the drug. When purchasing a drug under the PBS the maximum price a consumer pays is the patient co-payment contribution and those covered by government entitlements and those covered under the Repatriation Pharmaceutical Benefits Scheme have a reduced co-payment, which is $6.00 in 2014. The table below indicates the changes in co-payments over the years and these co-payments are compulsory and cannot be discounted by pharmacies under any circumstances. Private prescriptions are issued for medicines not covered on the PBS, or being used off-label, the patient pays the pharmacy for medicines privately prescribed. In the United Kingdom the Medicines Act 1968 and Prescription Only Medicines Order 1997 contain regulations that cover the supply of sale, use, prescribing is also covered by this legislation. A patient visits a medical practitioner or dentist authorised to prescribe drugs and certain other medical items, also, suitably qualified and experienced nurses and pharmacists may be independent prescribers. Both can prescribe all POMs but pharmacists are not allowed to prescribe schedule 1 controlled drugs, once issued, a prescription is taken by the patient to a pharmacy, which dispenses the medicine. Most prescriptions in the UK are NHS prescriptions, subject to a standard charge unrelated to what is dispensed, the NHS prescription fee was increased to £8. The pharmacy charges the NHS the actual cost of the medicine, a patient can consolidate prescription charges using a prescription payment certificate, effectively capping costs at £29.10 per quarter or £104.00 per year. Outside the NHS, private prescriptions are issued by private medical practitioners, NHS supply beyond three months worth is not covered, and must be purchased privately. A patient pays the pharmacy the normal price for medicine prescribed outside the NHS, in the United States, the Federal Food, Drug, and Cosmetic Act defines what substances require a prescription in order to be dispensed by a pharmacy. The Controlled Substances Act was enacted into law by the Congress of the United States in 1970, the CSA is the federal U. S. drug law under which the manufacture, importation, possession, use and distribution of certain substances is regulated. The legislation created five schedules with varying qualifications for a substance to be included in each, the safety and effectiveness of prescription drugs in the US is regulated by the federal Prescription Drug Marketing Act of 1987. The Food and Drug Administration is charged with implementing this law, misuse or abuse of prescription drugs can lead to adverse drug events, including those due to dangerous drug interactions

15.
National Collegiate Athletic Association
–
The National Collegiate Athletic Association is a non-profit association which regulates athletes of 1,281 institutions, conferences, organizations, and individuals. It also organizes the programs of many colleges and universities in the United States and Canada. The organization is headquartered in Indianapolis, Indiana, in 2014, the NCAA generated almost a billion dollars in revenue. 80 to 90% of this revenue was due to the Division I Mens Basketball Tournament and this revenue is then distributed back into various organizations and institutions across the United States. In August 1973, the current three-division setup of Division I, Division II, under NCAA rules, Division I and Division II schools can offer scholarships to athletes for playing a sport. Division III schools may not offer any athletic scholarships, generally, larger schools compete in Division I and smaller schools in II and III. Division I football was divided into I-A and I-AA in 1978. Subsequently, the term Division I-AAA was briefly added to delineate Division I schools which do not field a football program at all, in 2006, Divisions I-A and I-AA were respectively renamed the Football Bowl Subdivision and Football Championship Subdivision. Inter-collegiate sports began in the US in 1852 when crews from Harvard University, as other sports emerged, notably football and basketball, many of these same concepts and standards were adopted. Football, in particular, began to emerge as a marquee sport, the IAAUS was officially established on March 31,1906, and took its present name, the NCAA, in 1910. For several years, the NCAA was a group and rules-making body, but in 1921, the first NCAA national championship was conducted. Gradually, more rules committees were formed and more championships were created, a series of crises brought the NCAA to a crossroads after World War II. The Sanity Code – adopted to establish guidelines for recruiting and financial aid – failed to curb abuses, postseason football games were multiplying with little control, and member schools were increasingly concerned about how the new medium of television would affect football attendance. The complexity of problems and the growth in membership and championships demonstrated the need for full-time professional leadership. Walter Byers, previously an executive assistant, was named executive director in 1951. Byers wasted no time placing his stamp on the Association, as college athletics grew, the scope of the nations athletics programs diverged, forcing the NCAA to create a structure that recognized varying levels of emphasis. In 1973, the Associations membership was divided into three legislative and competitive divisions – I, II, and III, five years later in 1978, Division I members voted to create subdivisions I-A and I-AA in football. Until the 1980s, the association did not offer womens athletics, instead, the Association for Intercollegiate Athletics for Women, with nearly 1000 member schools, governed womens collegiate sports in the United States

16.
Urine
–
Urine is a liquid by-product of metabolism in the bodies of many animals, including humans. It is expelled from the kidneys and flows through the ureters to the urinary bladder, cellular metabolism generates numerous by-products, many nitrogenous, that require clearance from the bloodstream. These by-products are eventually expelled from the body during urination, the method for excreting water-soluble chemicals from the body. These chemicals can be detected and analyzed by urinalysis, of the many such substances that exist, the three main nitrogenous wastes of the mammalian body are urea, uric acid, and creatinine. Animal urine forms part of the nitrogen cycle, in balanced ecosystems it fertilizes soil and plants, which in turn continue to support the animal population. Some animals use it to mark their territories, human urine and human feces are collectively referred to as human waste, as sewage, they require sewage treatment in places where population density is high. Livestock urine and feces similarly require proper management if the population density is high. Such management is part of ecological sanitation, most animals have excretory systems for elimination of soluble toxic wastes. In humans, soluble wastes are excreted primarily by the system and, to a lesser extent in terms of urea. The urinary system consists of the kidneys, ureters, urinary bladder, the system produces urine by a process of filtration, reabsorption, and tubular secretion. The kidneys extract the soluble wastes from the bloodstream, as well as water, sugars. The resulting urine contains high concentrations of urea and other substances, urine flows from the kidney through the ureter, bladder, and finally the urethra before passing from the body. Research looking at the duration of urination in a range of species found that 9 larger species urinated for 21 ±13 seconds irrespective of body size. Smaller species including rodents and bats cannot produce jets and instead urinate with a series of drops, producing too much or too little urine needs medical attention. Polyuria is a condition of excessive production of urine, oliguria when <400 mL are produced, about 91-96% of urine consists of water. Urine also contains an assortment of inorganic salts and organic compounds, including proteins, hormones, the total solids in urine are on average 59 g per person per day. Organic matter makes up between 65% and 85% of urine dry solids, with volatile solids comprising 75–85% of total solids, urea is the largest constituent of the solids, constituting more than 50% of the total. On an elemental level, human urine contains 6.87 g/L carbon,8.12 g/L nitrogen,8.25 g/L oxygen, the exact proportions vary with individuals and with factors such as diet and health

17.
Doping in sport
–
The use of banned drugs to enhance performance is considered unethical, and therefore prohibited, by most international sports organizations, including the International Olympic Committee. Furthermore, athletes taking explicit measures to evade detection exacerbates the ethical violation with overt deception, historically speaking, the origins of doping in sports go back to the very creation of sport itself. From ancient usage of substances in chariot racing to more recent controversies in baseball and cycling, the general trend among authorities and sporting organizations over the past several decades has been to strictly regulate the use of drugs in sport. The reasons for the ban are mainly the health risks of performance-enhancing drugs, the equality of opportunity for athletes, anti-doping authorities state that using performance-enhancing drugs goes against the spirit of sport. There are many suggestions as to the origin of the term doping, one is that it is derived from dop, an alcoholic drink used as a stimulant in ceremonial dances in 18th century Southern Africa. By 1889, dope was used in connection with the preparation of a thick viscous preparation of opium for smoking, in 1900, dope was also defined as a preparation of drugs designed to influence the performance of a racehorse. The use of drugs in sports goes back centuries, about all the way back to the invention of the concept of sports. In ancient times, when the fittest of a nation were selected as athletes or combatants, they were fed diets, for instance, Scandinavian mythology says Berserkers could drink a mixture called butotens, to greatly increase their physical power at the risk of insanity. One theory is that the mixture was prepared from the Amanita muscaria mushroom, the ancient Olympics in Greece have been alleged to have been contaminated with forms of doping. In ancient Rome, where chariot racing had become a part of their culture. By April 1877, walking races had stretched to 500 miles, the event proved popular, however, with 20,000 spectators attending each day. The fascination with six-day bicycle races spread across the Atlantic and the appeal brought in the crowds in America as well. And the more spectators paid at the gate, the higher the prizes could be and their exhaustion was countered by soigneurs, helpers akin to seconds in boxing. Among the treatments they supplied was nitroglycerine, a used to stimulate the heart after cardiac attacks. Riders suffered hallucinations from the exhaustion and perhaps the drugs, the American champion Major Taylor refused to continue the New York race, saying, I cannot go on with safety, for there is a man chasing me around the ring with a knife in his hand. Public reaction turned against such trials, whether individual races or in teams of two and it appears from the reports of this singular performance that some of the bicycle riders have actually become temporarily insane during the contest. Days and weeks of recuperation will be needed to put the racers in condition, the father of anabolic steroids in the United States was John Ziegler, a physician for the U. S. weightlifting team in the mid-20th century. Ziegler learned from his Russian days that the Soviet weightlifting teams success was due to their use of performance-enhancing drugs, deciding that U. S. athletes needed chemical assistance to remain competitive, Ziegler worked with the CIBA Pharmaceutical Company to develop an oral anabolic steroid

18.
World Anti-Doping Agency
–
The World Anti-Doping Agency is a foundation initiated by the International Olympic Committee based in Canada to promote, coordinate and monitor the fight against drugs in sports. The aims of the Council of Europe Anti-Doping Convention are also aligned with those of WADA. The World Anti-Doping Agency is a foundation created through an initiative led by the International Olympic Committee. It was set up on November 10,1999 in Lausanne, Switzerland, as a result of what was called the Declaration of Lausanne, to promote, coordinate, since 2002, the organizations headquarters have been located in Montreal, Quebec, Canada. The Lausanne office became the office for Europe. Other regional offices have established in Africa, Asia/Oceania and Latin America. As of 2014, its president is Sir Craig Reedie, initially funded by the International Olympic Committee, WADA now receives half of its budgetary requirements from them, with the other half coming from various national governments. Its governing bodies are composed in equal parts by representatives from the sporting movement. The agencys key activities include research, education, development of anti-doping capacities. The highest decision-making authority in WADA is the 38-member foundation board, the Foundation Board appoints the agencys president. Most day-to-day management is delegated to a 12-member executive committee, membership of which is split equally between the IOC and governments. There also exist several sub-committees with narrower remits, including a Finance and Administration Committee and it delegates work in individual countries to Regional and National Anti-Doping Organizations and mandates that these organisations are compliant with the World Anti-Doping Code. WADA also accredits around 30 laboratories to perform the scientific analysis for doping control. The statutes of WADA and the World Anti-Doping Code mandate the Court of Arbitration for Sports ultimate jurisdiction in deciding doping-related cases, the Code is a document aiming to harmonize anti-doping regulations in all sports and countries. It embodies an annual list of prohibited substances and methods that sportspersons are not allowed to take or use, in 2004, the World Anti-Doping Code was implemented by sports organizations prior to the Olympic Games in Athens, Greece. In November 2007, more than 600 sports organizations unanimously adopted a revised Code at the Third World Conference on Doping in Sport, the updated code came into effect on January 1,2015. The Anti-Doping Convention of the Council of Europe in Strasbourg was opened for signature on December 16,1989 as the first multilateral legal standard in this field and it has been signed by 48 states including the Council of Europe and non-member states Australia, Belarus, Canada and Tunisia. The Convention is open for signature by other non-European states, in this sense the Convention strives for the same general aims as WADA, without being directly linked to it

19.
2004 Summer Olympics
–
10,625 athletes competed, some 600 more than expected, accompanied by 5,501 team officials from 201 countries. There were 301 medal events in 28 different sports, Athens 2004 marked the first time since the 1996 Summer Olympics that all countries with a National Olympic Committee were in attendance. 2004 marked the return of the games to the city where they began, a new medal obverse was introduced at these Games, replacing the design by Giuseppe Cassioli that had been used since the 1928 Games. This rectified the long lasting mistake of using a depiction of the Roman Colosseum rather than a Greek venue, the new design features the Panathenaic Stadium. The cost of the 2004 Athens Summer Games has been cited as a contributor to the Greek government-debt crisis, some of the venues lie vacant and rotting, while others are in use, the Independent newspaper reports as many as 21 out of 22 are unused. The final medal tally was led by the United States, followed by China, several World and Olympics records were broken during the games. Several concerns were raised over the preparations of the Games and these included excessive budget overruns, infrastructural compromise, the games were deemed generally successful with the rising standard of competition amongst nations across the world. Athens was chosen as the host city during the 106th IOC Session held in Lausanne on 5 September 1997, Athens had lost its bid to organize the 1996 Summer Olympics to Atlanta nearly seven years before on 18 September 1990, during the 96th IOC Session in Tokyo. 1996 coincided with the 100th Anniversary of the first modern Olympics, under the direction of Gianna Angelopoulos-Daskalaki, Athens pursued another bid, this time for the right to host the Summer Olympics in 2004. After leading all voting rounds, Athens easily defeated Rome in the 5th, cape Town, Stockholm, and Buenos Aires, the three other cities that made the IOC shortlist, were eliminated in prior rounds of voting. Six other cities submitted applications, but their bids were dropped by the IOC in 1996 and these cities were Istanbul, Lille, Rio de Janeiro, San Juan, Seville, Saint Petersburg and Cali. The 2004 Summer Olympic Games cost the Government of Greece €8.954 billion to stage, the Athens 2004 Organizing Committee, responsible for the preparation and organisation of the games, concluded its operations as a company in 2005 with a surplus of €130.6 million. ATHOC contributed €123.6 million of the surplus to the Greek State to cover other related expenditures of the Greek State in organizing of the games, as a result, ATHOC reported in its official published accounts a net profit of €7 million. The State’s contribution to the total ATHOC budget was 8% of its expenditure against an originally anticipated 14%, the overall revenue of ATHOC, including income from tickets, sponsors, broadcasting rights, merchandise sales etc. totalled €2,098.4 million. The largest percentage of income came from broadcasting rights. The overall expenditure of ATHOC was €1,967.8 million. e, the large projects required for the upgrade of the country’s infrastructure, including sports infrastructure, roads, airports, hospitals, power grid etc. This cost, however, is not directly attributable to the organisation of the Games. Such infrastructure projects are considered by all standards as fixed asset investments that stay with the hosting country for decades after the Games

20.
Athens
–
Athens is the capital and largest city of Greece. In modern times, Athens is a cosmopolitan metropolis and central to economic, financial, industrial, maritime. In 2015, Athens was ranked the worlds 29th richest city by purchasing power, Athens is recognised as a global city because of its location and its importance in shipping, finance, commerce, media, entertainment, arts, international trade, culture, education and tourism. It is one of the biggest economic centres in southeastern Europe, with a financial sector. The municipality of Athens had a population of 664,046 within its limits. The urban area of Athens extends beyond its administrative city limits. According to Eurostat in 2011, the Functional urban areas of Athens was the 9th most populous FUA in the European Union, Athens is also the southernmost capital on the European mainland. The city also retains Roman and Byzantine monuments, as well as a number of Ottoman monuments. Athens is home to two UNESCO World Heritage Sites, the Acropolis of Athens and the medieval Daphni Monastery, Athens was the host city of the first modern-day Olympic Games in 1896, and 108 years later it welcomed home the 2004 Summer Olympics. In Ancient Greek, the name of the city was Ἀθῆναι a plural, in earlier Greek, such as Homeric Greek, the name had been current in the singular form though, as Ἀθήνη. It was possibly rendered in the later on, like those of Θῆβαι and Μυκῆναι. During the medieval period the name of the city was rendered once again in the singular as Ἀθήνα, an etiological myth explaining how Athens has acquired its name was well known among ancient Athenians and even became the theme of the sculpture on the West pediment of the Parthenon. The goddess of wisdom, Athena, and the god of the seas, Poseidon had many disagreements, in an attempt to compel the people, Poseidon created a salt water spring by striking the ground with his trident, symbolizing naval power. However, when Athena created the tree, symbolizing peace and prosperity. Different etymologies, now rejected, were proposed during the 19th century. Christian Lobeck proposed as the root of the name the word ἄθος or ἄνθος meaning flower, ludwig von Döderlein proposed the stem of the verb θάω, stem θη- to denote Athens as having fertile soil. In classical literature, the city was referred to as the City of the Violet Crown, first documented in Pindars ἰοστέφανοι Ἀθᾶναι. In medieval texts, variant names include Setines, Satine, and Astines, today the caption η πρωτεύουσα, the capital, has become somewhat common

21.
Food and Drug Administration
–
The Food and Drug Administration is a federal agency of the United States Department of Health and Human Services, one of the United States federal executive departments. As of 2017, 3/4th of the FDA budget is funded by the pharmaceutical companies due to the Prescription drug user fee act and these include regulating lasers, cellular phones, condoms and control of disease on products ranging from certain household pets to sperm donation for assisted reproduction. The FDA is led by the Commissioner of Food and Drugs, appointed by the President with the advice, the Commissioner reports to the Secretary of Health and Human Services. Dr. Robert M. Califf, MD is the current commissioner, who took over in February 2016 for Dr. Stephen Ostroff, the FDA has its headquarters in unincorporated White Oak, Maryland. The agency also has 223 field offices and 13 laboratories located throughout the 50 states, the United States Virgin Islands, in 2008, the FDA began to post employees to foreign countries, including China, India, Costa Rica, Chile, Belgium, and the United Kingdom. The site was renamed from the White Oak Naval Surface Warfare Center to the Federal Research Center at White Oak, the first building, the Life Sciences Laboratory, was dedicated and opened with 104 employees on the campus in December 2003. Only one original building from the facility was kept. All other buildings are new construction, the project is slated to be completed by 2017, assuming future Congressional funding While most of the Centers are located in the Washington, D. C. The Office of Regulatory Affairs is considered the eyes and ears of the agency, the Office of Regulatory Affairs is divided into five regions, which are further divided into 20 districts. Districts are based roughly on the divisions of the federal court system. Each district comprises a main office and a number of Resident Posts. ORA also includes the Agencys network of laboratories, which analyze any physical samples taken. Though samples are usually food-related, some laboratories are equipped to analyze drugs, cosmetics, the Office of Criminal Investigations was established in 1991 to investigate criminal cases. Unlike ORA Investigators, OCI Special Agents are armed, and dont focus on aspects of the regulated industries. In many cases, OCI pursues cases involving Title 18 violations, OCI Special Agents often come from other criminal investigations backgrounds, and work closely with the Federal Bureau of Investigation, Assistant Attorney General, and even Interpol. OCI receives cases from a variety of sources—including ORA, local agencies, OCI is a smaller branch, comprising about 200 agents nationwide. The FDA frequently works with federal agencies, including the Department of Agriculture, Drug Enforcement Administration, Customs and Border Protection. Often local and state government agencies also work with the FDA to provide regulatory inspections, the FDA regulates more than US$1 trillion worth of consumer goods, about 25% of consumer expenditures in the United States

22.
Intensive farming
–
Intensive farming or intensive agriculture is any of various types of agriculture that involve higher levels of input and output per unit of agricultural land area. It is characterised by a low ratio, higher use of inputs such as capital and labour. This is in contrast to agriculture in which the inputs per unit land are lower. The term intensive has various senses, some of which refer to organic farming methods and others of which refer to nonorganic, both increase the yields of food and fiber per acre as compared to traditional animal husbandry. In CAFO, feed is brought to the animals, while in MIRG the animals are repeatedly moved to fresh forage. Most commercial agriculture is intensive in one or more ways, forms that rely especially heavily on industrial methods are often called industrial agriculture, which is characterised by innovations designed to increase yield. Techniques include planting multiple crops per year, reducing the frequency of fallow years, intensive farms are widespread in developed nations and increasingly prevalent worldwide. Most of the meat, dairy, eggs, fruits and vegetables available in supermarkets are produced by such farms, smaller intensive farms usually include higher inputs of labor and more often use sustainable intensive methods. The farming practices commonly found on farms are referred to as appropriate technology. These farms are widespread in both developed countries and worldwide, but are growing more rapidly. Most of the food available in specialty markets such as farmers markets is produced by these smallholder farms, agricultural development in Britain between the 16th century and the mid-19th century saw a massive increase in agricultural productivity and net output. This in turn supported unprecedented population growth, freeing up a significant percentage of the workforce, historians cited enclosure, mechanization, four-field crop rotation, and selective breeding as the most important innovations. Industrial agriculture arose along with the Industrial Revolution, by the early 19th century, agricultural techniques, implements, seed stocks and cultivars had so improved that yield per land unit was many times that seen in the Middle Ages. The industrialization phase involved a process of mechanization. Horse-drawn machinery such as the McCormick reaper revolutionized harvesting, while inventions such as the cotton gin reduced the cost of processing, during this same period, farmers began to use steam-powered threshers and tractors, although they were expensive and dangerous. Mechanical harvesters, planters, transplanters and other equipment were then developed and these inventions increased yields and allowed individual farmers to manage increasingly large farms. The identification of nitrogen, potassium, and phosphorus as critical factors in plant growth led to the manufacture of synthetic fertilizers, in 1909 the Haber-Bosch method to synthesize ammonium nitrate was first demonstrated. Farmers adopting this approach were initially referred to as humus farmers, chemicals developed for use in World War II gave rise to synthetic pesticides

23.
Bovine somatotropin
–
Bovine somatotropin or bovine somatotrophin, or bovine growth hormone, is a peptide hormone produced by cows pituitary glands. Like other hormones, it is produced in quantities and is used in regulating metabolic processes. Four large pharmaceutical companies, Monsanto, American Cyanamid, Eli Lilly, Monsanto was the first firm to receive approval. Other countries also approved rBST for commercial use, Monsanto licensed Genentechs patent, and marketed their product as Posilac. In October 2008, Monsanto sold this business, in full, to Eli Lilly, RBST has not been allowed on the market in Canada, Australia, New Zealand, Japan, Israel, or the European Union since 2000. Argentina also banned the use of rBST, the FDA, World Health Organization, and National Institutes of Health have independently stated that dairy products and meat from BST-treated cows are safe for human consumption. In the United States, public opinion led some manufacturers and retailers to market only milk that is rBST-free, in 1937, the administration of BST was shown to increase the milk yield in lactating cows by preventing mammary cell death in dairy cattle. Until the 1980s, use of the compound was very limited in agriculture as the source of the hormone was from bovine carcasses. During this time, the knowledge of the structure and function of the hormone increased, with the advent of biotechnology, one of the pioneering biotech companies, Genentech, succeeded in cloning the gene for BST. The two companies used genetic engineering to clone the BST gene into E. coli, the bacteria are grown in bioreactors, then broken up and separated from the rBST, which is purified to produce the injectable hormone. They published their first field trial results in 1981, Lilly, American Cyanamid, Upjohn, and Monsanto all submitted applications to market rBST to the U. S. Patrick Leahy. FDA approved Monsantos application in 1993, Monsanto launched rBST, brand-named Posilac, in 1994. An average dairy cow begins her lactation with a daily level of milk production. This daily output increases until, at about 70 days into the lactation, production peaks, from that time until the cow is dry, production slowly decreases. This increase and decrease in production is partially caused by the count of milk-producing cells in the udder, cell counts begin at a moderate number, increase during the first part of the lactation, then decrease as the lactation proceeds. Once lost, these generally do not regrow until the next lactation. The effects are mediated by the growth factor system, which is upregulated in response to BST or rBST administration in well-fed cows. From 2000-2005, the USDA National Agricultural Statistics Service survey of dairy producers found that about 17% of producers used rBST, the 2010 USDA National Agricultural Statistics Service survey of Wisconsin farms found that about 18% of dairy farms used rBST

24.
Human placental lactogen
–
Human placental lactogen, also called human chorionic somatomammotropin, is a polypeptide placental hormone, the human form of placental lactogen. Its structure and function are similar to those of growth hormone. It modifies the state of the mother during pregnancy to facilitate the energy supply of the fetus. HPL is a hormone secreted by the syncytiotrophoblast during pregnancy, like human growth hormone, hPL is encoded by genes on chromosome 17q22-24. HPL molecular mass is 22,125 and contains single chain consisting of 191 amino acid residues that are linked by two disulfide bonds and the structure contains 8 helices, maximum levels are reached near term, typically to 5–7 mg/L. Higher levels are noted in patients with multiple gestation, little hPL enters the fetal circulation. Its biological half-life is 15 minutes, HPL affects the metabolic system of the maternal organism in the following manners, In a bioassay hPL mimics the action of prolactin, yet it is unclear whether hPL has any role in human lactation. Metabolic ↓ maternal insulin sensitivity leading to an increase in blood glucose levels. ↓ maternal glucose utilization, which ensure adequate fetal nutrition. Chronic hypoglycemia leads to a rise in hPL. ↑ lipolysis with the release of fatty acids. With fasting and release of hPL, free fatty acids become available for the organism as fuel. Also, ketones formed from fatty acids can cross the placenta. These functions help support fetal nutrition even in the case of maternal malnutrition, an enhancer for the human placental lactogen gene is found 2 kb downstream of the gene and participates in the cell-specific control gene expression. While hPL has been used as an indicator of fetal well-being and growth, also, normal pregnancies have been reported with undetectable maternal levels of hPL. Placental lactogen in other species Somatotropin family RCSB Protein Data Bank - Structure Summary for 1Z7C - Crystal Structure of Human Placental Lactogen, Human Chorionic Somatomammotropin Enhancer Function Is Mediated by Cooperative Binding of TEF-1 and CSEF-1 to Multiple, Low-Affinity Binding Sites. Speroff L, Glass RH, Kase NG, hagerstwon, MD, Lippincott Williams & Wilkins. Human Placental Lactogen at the US National Library of Medicine Medical Subject Headings

25.
Prolactin
–
Prolactin, also known as luteotropic hormone or luteotropin, is a protein that is best known for its role in enabling mammals, usually females, to produce milk. It is influential in over 300 separate processes in various vertebrates, Prolactin is secreted from the pituitary gland in response to eating, mating, estrogen treatment, ovulation and nursing. Prolactin is secreted in pulses in between these events, Prolactin plays an essential role in metabolism, regulation of the immune system and pancreatic development. Discovered in non-human animals around 1930 by Oscar Riddle and confirmed in humans in 1970 by Henry Friesen prolactin is a peptide hormone and it is associated with human milk production. In fish it is thought to be related to control of water, Prolactin also acts in a cytokine-like manner and as an important regulator of the immune system. It has important cell cycle-related functions as a growth-, differentiating-, as a growth factor, binding to cytokine-like receptors, it influences hematopoiesis, angiogenesis and is involved in the regulation of blood clotting through several pathways. The hormone acts in endocrine, autocrine and paracrine manner through the prolactin receptor, pituitary prolactin secretion is regulated by endocrine neurons in the hypothalamus. Thyrotropin-releasing factor has an effect on prolactin release, however prolactin is the only adenohypophyseal hormone whose principal control is inhibitory. Several variants and forms are known per species, many fish have variants prolactin A and prolactin B. Most vertebrates including humans also have the closely related somatolactin, in humans, three smaller and several larger variants exist. Prolactin has a variety of effects. Sometimes, newborns secrete a substance from their nipples known as witchs milk. This is in part caused by maternal prolactin and other hormones, Prolactin plays an important role in maternal behavior. Prolactin provides the body with sexual gratification after sexual acts, The hormone counteracts the effect of dopamine and this is thought to cause the sexual refractory period. The amount of prolactin can be an indicator for the amount of satisfaction and relaxation. Unusually high amounts are suspected to be responsible for impotence and loss of libido, elevated levels of prolactin decrease the levels of sex hormones — estrogen in women and testosterone in men. The effects of elevated levels of prolactin are much more variable, in women. Prolactin is sometimes classified as a gonadotropin although in humans it has only a weak luteotropic effect while the effect of suppressing classical gonadotropic hormones is more important, Prolactin within the normal reference ranges can act as a weak gonadotropin, but at the same time suppresses GnRH secretion

26.
Atomic mass unit
–
The unified atomic mass unit or dalton is a standard unit of mass that quantifies mass on an atomic or molecular scale. One unified atomic mass unit is approximately the mass of one nucleon and is equivalent to 1 g/mol. The CIPM has categorised it as a non-SI unit accepted for use with the SI, the amu without the unified prefix is technically an obsolete unit based on oxygen, which was replaced in 1961. However, many still use the term amu but now define it in the same way as u. In this sense, most uses of the atomic mass units. For standardization a specific atomic nucleus had to be chosen because the mass of a nucleon depends on the count of the nucleons in the atomic nucleus due to mass defect. This is also why the mass of a proton or neutron by itself is more than 1 u, the atomic mass unit is not the unit of mass in the atomic units system, which is rather the electron rest mass. The relative atomic mass scale has traditionally been a relative value and this evaluation was made prior to the discovery of the existence of elemental isotopes, which occurred in 1912. The divergence of these values could result in errors in computations, the chemistry amu, based on the relative atomic mass of natural oxygen, was about 1.000282 as massive as the physics amu, based on pure isotopic 16O. For these and other reasons, the standard for both physics and chemistry was changed to carbon-12 in 1961. The choice of carbon-12 was made to minimise further divergence with prior literature. The new and current unit was referred to as the atomic mass unit u. and given a new symbol, u. The Dalton is another name for the atomic mass unit. 1 u = m u =112 m Despite this change, modern sources often use the old term amu but define it as u. Therefore, in general, amu likely does not refer to the old oxygen standard unit, the unified atomic mass unit and the dalton are different names for the same unit of measure. As with other names such as watt and newton, dalton is not capitalized in English. In 2003 the Consultative Committee for Units, part of the CIPM, recommended a preference for the usage of the dalton over the atomic mass unit as it is shorter. In 2005, the International Union of Pure and Applied Physics endorsed the use of the dalton as an alternative to the atomic mass unit

27.
Species
–
In biology, a species is the basic unit of biological classification and a taxonomic rank. A species is defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is problematic, for example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Other ways of defining species include similarity of DNA, morphology, all species are given a two-part name, a binomial. The first part of a binomial is the genus to which the species belongs, the second part is called the specific name or the specific epithet. For example, Boa constrictor is one of four species of the Boa genus, Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped that species could evolve given sufficient time, Charles Darwins 1859 book The Origin of Species explained how species could arise by natural selection. Genes can sometimes be exchanged between species by horizontal transfer, and species may become extinct for a variety of reasons. In his biology, Aristotle used the term γένος to mean a kind, such as a bird or fish, a kind was distinguished by its attributes, for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance, when observers in the Early Modern period began to develop systems of organization for living things, they placed each kind of animal or plant into a context. Many of these early delineation schemes would now be considered whimsical, animals likewise that differ specifically preserve their distinct species permanently, one species never springs from the seed of another nor vice versa. In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics and he established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships. At the time, however, it was widely believed that there was no organic connection between species, no matter how similar they appeared. However, whether or not it was supposed to be fixed, by the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time, in 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals and this required a new definition of species. Darwin concluded that species are what appear to be, ideas

28.
Old World monkey
–
The Old World monkeys or Cercopithecidae are a family of catarrhines, the only family in the superfamily Cercopithecoidea in the clade of Catarrhini. However, a group of monkeys still survives in Gibraltar to this day. Old World monkeys include many of the most familiar species of primates, such as baboons. Old World monkeys are medium to large in size, and range from arboreal forms, such as the monkeys, to fully terrestrial forms. By superficial appearance, Old World monkeys are unlike apes in that most have tails and, unlike the New World monkeys, technically, the distinction of catarrhines from platyrrhines depends on the structure of the nose, and the distinction of Old World monkeys from apes depends on dentition. In platyrrhines, the nostrils face sideways, while in catarrhines, for example, the colobus monkeys have stubs for thumbs to assist with their arboreal movement, the proboscis monkey has an extraordinary nose, while the snub-nosed monkeys have almost no nose at all. The male mandrills penis is red and the scrotum is lilac, the coloration is more pronounced in dominant males. Most Old World monkeys are at least partially omnivorous, but all prefer plant matter, the Barbary macaques diet consists mostly of leaves and roots, though it will also eat insects and uses cedar trees as a water source. Gestation in the Old World monkeys lasts between five and seven months, births are usually single, although, as with humans, twins occur from time to time. The young are born relatively well-developed, and are able to cling onto their mothers fur with their hands from birth, compared with most other mammals, they take a long time to reach sexual maturity, with four to six years being typical of most species. In most species, daughters remain with their mothers for life, males leave the group on reaching adolescence, and find a new troop to join. In many species, only an adult male lives with each group, driving off all rivals. Group sizes are variable, even within species, depending on the availability of food. Therefore, cladistically, apes, catarrhines and related contemporary extinct groups such as Parapithecidaea are monkeys as well, for any consistent definition of monkey

29.
Growth hormone receptor
–
Growth hormone receptor is a protein that in humans is encoded by the GHR gene. GHR orthologs have been identified in most mammals and this gene encodes a protein that is a transmembrane receptor for growth hormone. Binding of growth hormone to the leads to receptor dimerization. A common alternate allele of this gene, called GHRd3, lacks exon three and has been well-characterized, mutations in this gene have been associated with Laron syndrome, also known as the growth hormone insensitivity syndrome, a disorder characterized by short stature. Other splice variants, including one encoding a soluble form of the protein, have observed but have not been thoroughly characterized. Laron mice, have a reduction in body mass. Growth hormone receptor has shown to interact with SGTA, PTPN11, Janus kinase 2, Suppressor of cytokine signaling 1. The GHR gene is used in animals as a nuclear DNA phylogenetic marker, the exon 10 has first been experienced to explore the phylogeny of the major groups of Rodentia. GHR has also proven useful at lower levels, e. g. in octodontoid, arvicoline, muroid, murine, and peromyscine rodents, in arctoid and felid carnivores. Note that the GHR intron 9 has also used to investigate the mustelid and hyaenid carnivores phylogenetics. Growth hormone receptor antagonists such as pegvisomant are used in the treatment of acromegaly and they are used if the tumor of the pituitary gland causing the acromegaly cannot be controlled with surgery or radiation, and the use of somatostatin analogues is unsuccessful. Pegvisomant is delivered as a powder that is mixed with water and injected under the skin

30.
Molecule
–
A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge, however, in quantum physics, organic chemistry, and biochemistry, the term molecule is often used less strictly, also being applied to polyatomic ions. In the kinetic theory of gases, the molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are in fact monoatomic molecules. A molecule may be homonuclear, that is, it consists of atoms of one element, as with oxygen, or it may be heteronuclear. Atoms and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are not considered single molecules. Molecules as components of matter are common in organic substances and they also make up most of the oceans and atmosphere. Also, no typical molecule can be defined for ionic crystals and covalent crystals, the theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding, which means that solid metals are also not made of molecules. In glasses, atoms may also be together by chemical bonds with no presence of any definable molecule. The science of molecules is called molecular chemistry or molecular physics, in practice, however, this distinction is vague. In molecular sciences, a molecule consists of a system composed of two or more atoms. Polyatomic ions may sometimes be thought of as electrically charged molecules. The term unstable molecule is used for very reactive species, i. e, according to Merriam-Webster and the Online Etymology Dictionary, the word molecule derives from the Latin moles or small unit of mass. Molecule – extremely minute particle, from French molécule, from New Latin molecula, diminutive of Latin moles mass, a vague meaning at first, the vogue for the word can be traced to the philosophy of Descartes. The definition of the molecule has evolved as knowledge of the structure of molecules has increased, earlier definitions were less precise, defining molecules as the smallest particles of pure chemical substances that still retain their composition and chemical properties. Molecules are held together by covalent bonding or ionic bonding. Several types of non-metal elements exist only as molecules in the environment, for example, hydrogen only exists as hydrogen molecule. A molecule of a compound is made out of two or more elements, a covalent bond is a chemical bond that involves the sharing of electron pairs between atoms

A fluorescent image of an endothelial cell. Nuclei are stained blue, mitochondria are stained red, and microfilaments are stained green.

Human cancer cells with nuclei (specifically the DNA) stained blue. The central and rightmost cell are in interphase, so the entire nuclei are labeled. The cell on the left is going through mitosis and its DNA has condensed.

Medical Officer Alexander Fleming, M. D., examines a portion of a 240-volume new drug application around the late 1980s. Applications grew considerably after the efficacy mandate under the 1962 Drug Amendments.

Satellite image of circular crop fields in Haskell County, Kansas, in late June 2001. Healthy, growing crops of corn and sorghum are green (sorghum may be slightly paler). Wheat is brilliant gold. Fields of brown have been recently harvested and plowed under or have lain in fallow for the year.

Construction of recombinant DNA, in which a foreign DNA fragment is inserted into a plasmid vector. In this example, the gene indicated by the white color is inactivated upon insertion of the foreign DNA fragment.